1. Technical Field of the Invention
The present invention relates generally to a stator which may be installed in a motor-generator or an AC generator for use in automotive vehicles such as electric vehicles or hybrid vehicles.
2. Background Art
Japanese Patent First Publication No. 11-341730 discloses a stator of an electric rotating machine. The stator is equipped with a stator core facing a rotor and a stator winding wound in the stator core. The stator core has a plurality of slots formed therein. The stator winding is made up of a plurality of conductor segments each of which includes in-slot portions disposed within the slots of the stator core and coil end portions extending from the slot outside either of axially-opposed ends of the stator core. The coil end portions are welded to make a teardrop-shaped joint without any sharp edges. The joints are arrayed at a regular interval away from each other in a circular form and coated with insulating resin to achieve electric insulation between the joints themselves or between the joints and peripheral members such frames of a housing of an AC generator.
The electric rotating machine, as disclosed in the above publication, has a cooling fan installed on the rotor to cool the joints which are subjected to high temperature during running of the electric rotating machine. The cooling fan works to blow cooling air from inside the inner periphery of the array of the joints toward air outlets formed in a frame disposed outside the array of the joints to create cooling air hits on the joints. The cooling air usually contains dust or numerous impurities from the atmosphere. The hits of the cooling air on the joints may result in physical damages to the insulating coating on the joints. The insulating coating is of a teardrop-shape contoured to conform with the joint and soft in hardness. The hits of the cooling air or the impurities on the joints may, therefore, result in removal of the insulating coating from the joints, which leads to a failure in insulation between the joints themselves or between the joints and the peripheral member.